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.Dd April 18, 2021
.Dt GETPROGNAME 3
.Os
.Sh NAME
.Nm getprogname ,
.Nm setprogname
.Nd get or set the program name
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft const char *
.Fn getprogname "void"
.Ft void
.Fn setprogname "const char *progname"
.Sh DESCRIPTION
The
.Fn getprogname
and
.Fn setprogname
functions manipulate the name of the current program.
They are used by error-reporting routines to produce
consistent output.
.Pp
The
.Fn getprogname
function returns the name of the program.
If the name has not been set yet, it will return
.Dv NULL .
.Pp
The
.Fn setprogname
function sets the name of the program to be the last component of the
.Fa progname
argument.
Since a pointer to the given string is kept as the program name,
it should not be modified for the rest of the program's lifetime.
.Pp
In
.Fx ,
the name of the program is set by the start-up code that is run before
.Fn main ;
thus,
running
.Fn setprogname
is not necessary.
Programs that desire maximum portability should still call it;
on another operating system,
these functions may be implemented in a portability library.
Calling
.Fn setprogname
allows the aforementioned library to learn the program name without
modifications to the start-up code.
.Sh EXAMPLES
The following example presents a simple program, which shows the difference
between
.Fn getprogname
and
.Va "argv[0]" .
.Bd -literal -offset indent
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char** argv)
{
	printf("getprogname(): %s\en", getprogname());
	printf("argv[0]: %s\en", argv[0]);
	return (0);
}
.Ed
.Pp
When compiled and executed (e.g., with
.Ql ./a.out )
the output of the program is going to look like this:
.Bd -literal -offset indent
getprogname(): a.out
argv[0]: ./a.out
.Ed
.Sh SEE ALSO
.Xr err 3 ,
.Xr setproctitle 3
.Sh HISTORY
These functions first appeared in
.Nx 1.6 ,
and made their way into
.Fx 4.4 .
